Scrapers for pelletizing disks

ABSTRACT

An improved scraper for pelletizing disks is disclosed. The scraper edge is made of a silicon carbide material whereby the cost per unit wear is substantially reduced yet there is little or no loss in efficiency of operation.

United States Patent Skretting et al.

SCRAPERS FOR PELLETIZING DISKS Inventors: Hans Skretting, Vagsbygd; Ole Egeland, Kristiansand, both of Norway Assignee: Elkem-Skigerverket A/S, Oslo,

Norway Filed: Apr. 10, 1974 Appl. No.: 459,608

Foreign Application Priority Data Apr. 13, 1973 Norway 1545/73 US. Cl. 425/225, 425/331 Int. Cl. B296 1/00 Field of Search 425/225, 331, 77

[ Mar. 11, 1975 [56] References Cited UNITED STATES PATENTS 2,941,248 6/1960 Hall 425/77 3,199,465 8/1969 Cunningham 425/331 3,407,756 10/1968 Morse 425/331 3,581,678 6/1971 Landers 425/331 X 3,743,462 7/1973 Alessio 425/331 X Primary Examiner.l. Howard Flint, Jr. Attorney, Agent, or FirmEyre, Mann & Lucas [57] ABSTRACT An improved scraper for pelletizing disks is disclosed. The scraper edge is made of a silicon carbide material whereby the cost per unit wear is substantially reduced yet there is little or no loss in efficiency of operation.

3 Claims, 1 Drawing Figure SCRAPERS FOR PELLETIZING DISKS The present invention relates to pelletizing disks. As

is well known in the art, pelletizing disks are used to convert finely divided materials such as ore concentrates into pellets whereby their use value is markedly increased as for example if they are to be used in electric smelting furnaces. As is also well known, these pelletizing disks employ one or more scraping members in order to maintain the bottom and side walls of the pelletizing disk clean, and also to prevent piling up of the finely divided material thereby reducing pelletizing efficiency. In some instances the scrapers are stationary whereas in others they rotate.

The actual scraping surface of each scraper is usually formed of a very hard metal in order to reduce wear on the scraping surface. Typical of these hard metals are sintered tungsten/cobalt carbide alloys. However, hard metals such as sintered tungsten/cobalt carbide alloys are very expensive to buy and the expense in terms of wear of using such materials can about to $30-70 or even more per 100 tons of pellets produced depending upon the particular hard metal and the particular finely divided material being pelletized. This is quite a substantial expense and it would be highly beneficial to be able to reduce this expense.

The applicant has now discovered that it is possible to employ silicon carbide as the scraping material. This results in a very substantial monetary savings as is evi- (a) a tungsten/cobalt carbide alloy available from Stavanger Staal, Jj arpeland, Norway (b) a tungsten/cobalt carbide alloy available from Johns. Sandvik, division of Elkem-Spigerverket, Oslo, Norway (c) a silicon carbide available from Borgestad Fabrikker NS, 3910,

Borgestad,Norway i As can be seen from the table, the savings when using silicon carbide in accordance with the present invention are very substantial.

In accordance with the present invention, the silicon carbide is utilized in rod form in a surrounding tube of steel as is shown in the FIGURE. The silicon carbide rod is embedded in a surrounding tube suitably of steel 12. The silicon carbide rod 10 is suitably affixed to the steel tube 12 by means of molten sulphur or other similar known attachment means. The surrounding tubular holder 12 is preferably open as shown at 13 at the working surface of the silicon carbide rod 10 so that the annular surface 14 of the silicon carbide rod 10 is in contact with the pelletizing disk 16 to effect the necessary scraping action. The scraper is held in position by suitably adjustable means (not shown). As the silicon carbide surface 14 wears away, the entire assembly of the scraper 18 is lowered towards the pelletizing disk 16. The metal tube 12 will of course wear away but this will not be at all deleterious to continuing the scraping effect of the silicon carbide rod 10 and in fact will help to support the silicon carbide rod throughout its useful life.

In addition to the substantial cost saving when silicon carbide is employed as taught in the instant invention, it is also pointed out that its wear characteristics are such that it does not create a replacement problem. There are, of course, many materials which are cheaper than tungsten/cobalt carbide alloys but it is necessary that the scraper material not only be less expensive but that it also have good wear characteristics so that it is not necessary to stop the machine and adjust or replace the scraper element at unduly short intervals. It has been found that the silicon carbide scrapers of the instant invention will last for approximately 2 weeks before they need adjustment which, as a practical matter. means that they need to be adjusted only when the machine is ordinarily stopped for servicing.

It will be understood that the claims are intended to cover all changes and modifications of the preferred embodiments of the invention, herein chosen for the purpose of illustration, which do not constitute departures from the spirit and scope of the invention.

What is claimed is:

1. In a pelletizing disk apparatus for the formation of pellets from finely divided material comprising a pelletizing disk and at least one scraper, the improvement comprising having the working edge of the scraper composed of a silicon carbide rod rigidly affixed in a surrounding tubular holder.

2. The apparatus of claim 1 wherein the surrounding tubular holder is steel.

3. The apparatusof claim 1 wherein the surrounding tubular holder is open on the working surface of the scraper. 

1. In a pelletizing disk apparatus for the formation of pellets from finely divided material comprising a pelletizing disk and at least one scraper, the improvement comprising having the working edge of the scraper composed of a silicon carbide rod rigidly affixed in a surrounding tubular holder.
 1. IN A PELLETIZING DISK APPARATUS FOR THE FORMATION OF PELLETS FROM FINELY DIVIDED MATERIAL COMPRISING A PELLETIZING DISK AND AT LEAST ONE SCRAPER, THE IMPROVEMENT COMPRISING HAVING THE WORKING EDGE OF THE SCRAPER COMPOSED OF A SILICON CARBIDE ROD RIGIDLY AFFIXED IN A SURROUNDING TUBLAR HOLDER.
 2. The apparatus of claim 1 wherein the surrounding tubular holder is steel. 